"Specific Entropy" is entropy per unit of mass.
Applicable units are those of quantitykind:SpecificEntropy
http://dbpedia.org/resource/Entropy
"Specific Entropy" is entropy per unit of mass.
$s = S/m$, where $S$ is entropy and $m$ is mass.
http://www.iso.org/iso/catalogue_detail?csnumber=31890